As someone who used to get paid for this sort of thing (database
performance tuning) it did make a difference, I would however agree that
on a modern windows systems with modern large disks it would make little
difference. It's really amazing how much things have changed in recent
years.
For those who want to know
this was taken from
<http://www.ibm.com/developerworks/aix/library/au-aixoptimization-disktun2/index.html>
*Figure 2. Actual storage position on the physical disk platter*
Actual storage position on the physical disk platter
As a general rule, data that is written toward its center has faster
seek times than data written on the outer edge. This has to do with the
density of data. Because it is more dense as it moves toward its center,
there is actually less movement of the head. The inner edge usually has
the slowest seek times. As a best practice, the more intensive I/O
applications should be brought closer to the center of the physical
volumes. Note that there are exceptions to this. Disks hold more data
per track on the edges of the disk, not on the center. That being said,
logical volumes being accessed sequentially should actually be placed on
the edge for better performance. The same holds true for logical volumes
that have Mirror Write Consistency Check (MWCC) turned on. This is
because the MWCC sector is on the edge of the disk and not at the center
of it, which relates to the intra-disk policy of logical volumes.
Let's discuss another important concept referred to as the inter-disk
policy of logical volumes. The inter-disk policy defines the number of
disks on which the physical partitions of a logical volume actually
resides. The general rule is that the minimum policy provides the
greatest reliably and availability, and the maximum policy improves
performance. Simply put, the more drives that data is spread on, the
better the performance. Some other best practices include: allocating
intensive logical volumes to separate physical volumes, defining the
logical volumes to the maximum size you need, and placing logical
volumes that are frequently used close together. This is why it is so
important to know your data prior to configuring your systems so that
you can create policies that make sense from the start.
On 14/08/2012 21:33, Jim Nichols wrote:
> Hi Chuck,
>
> With modern, large drives, I have seen no improvements in the rare occasions
> I have run a defrag program. And, with the increase in drive capacities, it
> would take forever to complete a defrag effort. I agree, snake oil!
>
>
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